The present invention generally relates to lasers and, more particularly, to a two-piece laser cathode assembly with an end cap having a concave interior surface providing uniform equipotential discharge characteristics.
A conventional gas discharge laser, such as a helium-neon gas laser, typically includes an outer envelope which mounts components at its opposite ends defining an anode and a cathode. End mirrors are mounted adjacent opposite ends of the envelope by the anode and cathode components, and a bore tube is mounted within the envelope and in alignment with the end mirrors. The bore tube and end mirrors are precisely aligned along a common, central axis to form an optical resonant cavity and produce optimum lasing action.
The lasing action which produces the laser beam takes place in the bore tube between the end mirrors as a high voltage direct current is applied between the anode and cathode and through a mixture of helium and neon gases being contained in the outer envelope at a small fraction of atmospheric pressure. Application of the high voltage direct current produces a discharge which flows from the anode through the bore tube and from the free end of the bore tube to the spaced cathode.
Heretofore, the construction of the laser cathode has ordinarily been in the form of a two-piece cylindrical cathode tube and a flat end cap. The flat configuration of the end cap has tended to cause a nonuniform, localized discharge being concentrated more at the central region of the end cap than at the peripheral region thereof. Such nonuniform discharge distribution shortens the life of the cathode and thereby reduces the longevity of the laser.
Those cathode designs in the prior art which have employed two-piece constructions have not specifically dealt with the problem of nonuniform discharge. On the other hand, the concept of uniform distribution of electrical discharge has been addressed heretofore in a one-piece cathode construction, wherein an internal spherical surface was provided on the end of the one-piece cathode. However, the one-piece cathode was fabricated by a deep-drawing process which was expensive and difficult to carry out satisfactorily. Therefore, the one-piece cathode approach did not prove to be an acceptable answer to the problem of nonuniform discharge.
In view of the above-described shortcomings of prior art cathode construction, a need still remains for an alternative approach to cathode design and construction which addresses and resolves the outstanding problem of nonuniform electrical discharge distribution.